Noise suppressor for radio receivers



pril 21, 1936. E A ZADlG NOISE SUPPRESSOR FOR RADIO RECEIVEBS Filed Deo.

m H. 0 5 m. m v, m 2 3 m m M7. T. NM wg m N R E BW@ WW ATTORNEY Patented Apr. 21, 1936 UNITEDA STATES PATENT oFFicE NOISE SUPPRESSOR FOR RADIO RECEIVERS Application December 5, 1930, Serial No. 500,218 13 Claims. v.(Cl. Z50-20) My present invention relates to radio signalling devices, and more particularly to novel arrangements for controlling the reproducer of a radio receiver during the adjustment of the signal selecting means.

Experience with radio receivers has demonstrated that there exists a need for rendering the reproducer of a receiver inoperative during certain operations. For example, it is a well known fact that the selecting, or tuning, operation of a receiver is often accompanied by the production of a great deal of noise. The latter, in many cases, comprise the reproduced signals of stations between two given tuning points, the

l5 hasty tuning and detuning in such cases resulting in exceedingly disagreeable sounds. Should such intermediate signals be of relatively great intensity, then the discordant eiect is increased. Again, such noise may include reproduced static which may happen to lie between two given tuning points. The effect of static on the listener is too wellknown to require explanation. When an automatic volume control device is used in conjunction with a receiver, between-station noises, and especially static noises, are greatly amplified, and become vexatious to the ear of the listener.

Now, I have discovered a method of, and means for, obviating the reproduction of all types of undesired between-station noises during the tuning operation of a radio receiver. The device is so arranged that the signal reproducer becomes inoperative the moment the manually-operable tuning means is actuated, the reproducer becom- 35 ing operative again the instant that the tuning means is rendered immobile. Hence, the noise protection afforded by the present device is entirely independent of logged stations.

To emphasize the need, desirability and par- 40 ticular utility of the present invention, it is pointed out that the necessity for cutting out the reproducer during tuning is especially marked in a manually tuned receiver, since the betweenstation noises in such receivers are greater than in motor-tuned sets in view of the relatively smaller speed of adjustment of the manually tuned set.

Accordingly, it is one of the main objects of my present invention to provide a method of,

50 and means for, suppressing eiects, undesirable to the user oi a radio receiver, produced during selective signal adjustment of a receiver, the method comprising rendering the receiver reproducer inoperative throughout the aforemen- 55 tioned adjustment.

Another important object of the present invention is to provide a noise suppressor, operable simultaneously with the tuning control, for a radio receiver comprising an arrangement mechanically associated with the said control in such 5 a manner that the reproducer is rendered inoperative the instant the control is motivated, remaining inoperative as long as the control is operative, and becoming operative again the instant the control is rendered inoperative. 10

Another object of the invention is to provide in combination with manually-actuable tuning control of a radio receiver, whether the tuning control be disposed at the receiver panel or remote therefrom, a device so related to the control that the loud speaker, or any other type of electric signal reproducer, is rendered inoperative, and maintained inoperative, from the instant the control is manually actuated to the instant the Ycontrol is'rendered inoperative, whereby all effects 20 undesirable to the operator of the receiver, and existing between the aforementioned control actuation points, are not reproduced.

Still other objects of the present invention are to improve generally the eiiiciency and appreciation of radio receivers, and to more particularly provide an improved arrangement for suppressing undesirable between-station effects during the tuning of a receiver, such arrangement being simple in design, durable and reliable in operation, and economical in manufacture and installation.

rIhe novel features which I believe to be characteristic of my invention are set `forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several constructions whereby my invention may be carried into effect.

In the drawing,

Fig. l shows, in partial section, an arrangement embodying the present invention,

Fig. 2 shows, in partial section, a modiiied arrangement of the invention, and 4,5 Fig. 3 shows a side elevational view of the tuning shaft disclosed in either Fig. 1 or Fig. 2, and the association therewith of certain cooperating elements.

Referring now to the accompanying drawing in which like characters of reference indicate the same parts in the different iigures, there is shown in Fig. 1 an embodiment of the invention wherein the reproducer of a radio receiver is rendered inoperative during the tuning operation of the receiver by opening the energizing, or exciting, circuit of the reproducer diaphragm I of the loud speaker. For the purpose of illustration only, and without intending any limitation, the reproducer is shown as'comprising an electrodynamic loud speaker, the latter including the usual energizing eld coil 2, and the signal coil 3, the latter being connected to any source of signals desired to be reproduced.

As is well known in the prior art the source of signals may be a conventional radio receiver, the coil 3 in that case being connected to the output of the last audio amplifier stage. The speaker need be described in no further detail, except to point out that the coil 3 is mounted for movement with the diaphragm I, the coil 2 being relatively immobile. Energizing current flows through the eld coil 2 from a source of current 4.

The source 4 may be derived from any conventional power supply, and is so Well known to those skilled in the art, that it will suffice to point out that when current from source 4 flows through the coil 2, then, if signal current flows through the coil 3 from the receiver, the diaphragm I will reproduce such signals. In order to render the source 4 inoperative, during tuning, to excite coil 2, I have provided a simple and highly eiicient switch mechanism in association with the usual tuning shaft 5 of the aforementioned receiver.

It will be understood that the reference numeral 5 represents the conventional common, gang condenser shaft upon which the rotor plates of the gang of condensers are mounted. This is diagrammatically illustrated in Fig. 3. The shaft, of course, is adjusted, or actuated, by turning a knob, such as 5, upon the panel of the receiver, the knob being usually mechanically connected to the shaft 5 in any number of ways too numerous to detail. Thus, as is well understood, to select a particular station, it is only necessary to rotate the shaft 5 clock-Wise, or counter-clockwise, thereby adjusting the rotor plates of the condensers, in the well known manner, to select desired signals for reproduction by the diaphragm I.

In order to render ineffective the exciting effect of the source 4, whenever the. shaft 5 is actuated,

the shaft 5 is in motion, a pendulum contact member 6 is mounted upon the shaft 5. The contact member comprises a perforated friction disc portion 1, the inner periphery 8 of which perforation contacts with the outer periphery of the shaft 5 for approximately its entire circumference.

6 consists of the extension 9, the latter extending portion as shown. An adjusting slot I0 is provided between the lower portion of the extension 9 and the inner periphery of the disc '1. A threaded screw I I is secured in one side of the slot I8, and is embedded in the other side., the slotted head of the screw being exposed in order to facilitate regulation of the amount of slip between the disc periphery 8 and the. shaft periphery.

The pendulum member 6 can be made of any desired insulation material, such as a phenolic condensation product, hard rubber, or fabric imthe aforementioned materials. The member can, of course, be stamped out in one operation to produce the shape shown, and provide the perforation and adjusting slot I8.

A pair of independent, flexible and highly resilient switch prongs I2, I3, are disposed adjacent the extension 9. Each of the prongs is secured, in any desired manner, at one end thereof to the head of a T-shaped insulation support I4, the latter being constructed of any well known insulation material, as for example those already noted in connection with the pendulum member 6. The lower end of each prong is` slightly offset so that the lower ends are disposed closer together than the upper ends thereof, the extension 9 being disposed substantially midway between the, lower, oset ends of the prongs.

The depending portion I5 of the support I4 has Xedly embedded therein a metallic connector pin I6 provided with a metallic head Il on either end of the said pin. Each head I I is.` exposed and abuts the face of the depending portion I5 which abuts it.

Each prong I2 and I3 is, additionally, provided with a metallic, each contact being in contact with an adjacent disposed between the prongs and is not urged thereagainst. That is to say, when the shaft 5 is immobile, the normal position of the member S is such that the extension 9 is in non-contacting relation with, and rests between, the lower ends of the prongs I2 and I3, while the contacts I 8 each abut their respective heads I l.

To complete the energizing circuit, the prong i3 is connected at its upper end, through a conductor I 9, to one terminal of the field coil 2. 'I'he opposite prong end is connected, through a conductor 28, to one terminal of the source 4, it being thus seen that the source 4 is connected in series with the coil 2 and prongs I2, I3.

It will now be realized that actuation of the shaft 5, caused for example by rotating the tuning knobon the receiver panel in either direction, results in opening the field coil circuit, by virtue of the fact that the ilow of current from the prong I2 to the prong I3 through the heads I1 and connector pin I 6 is interrupted. It will be understood that the prongs I2 and I3 are made suiciently resilient so as to enable them to restore the pendulum member 6 to its normal intermediate position, whenever the shaft 5 is rendered immobile.

In operation, therefore, it will be seen that the reproducer becomes inoperative the moment the I movement ceases. The noise protection afforded by the device, therefore, becomes entirely indestations. Adjustment of the. screw I I regulates the necessary amount of slip between the friction disc portion 'I and the shaft 5.

Preferably, the amount of slip is so chosen that extension 9 and the lower end of either prong results in the immediate opening of the field coil circuit by virtue of the failure of contact between a Contact I8 and a head Il.

On the other hand, each prong must be made suiciently resilient to constantly oppose the continued movement of the pendulum extension 9 in a given direction, once a Contact I8 and head I'I have been separated. It will thus be seen that at this point the shaft 5 is in motion, while the pendulum member 6 is relatively immobile, the

conical contact I8, the apex of amountof friction being developed being suiicient to maintain equilibrium between the resilient opposing force in a prong and the aforementioned frictional force. Obviously, as soon as movement of the shaft 5 stops, the unopposed resilient force of a prong will instantly restore the extension 9 of the pendulum member 6 to its normal intermediate position.

In Fig. 2, I have shown a modification of the arrangement shown in Fig. 1, the pendulum member 6 being of the same construction as shown in Fig. 1. In this case, however, it is desired to short-circuit the energizing circuit of the voice coil 3, this being accomplished by constructing the prongs I2 and I3 relatively rigid. This is preferably accomplished by bending a metallic strip into a U-shaped configuration, the bend of the strip 2| being connected through a conductor 22 to a conductor 23, the latter conductor also being connected at one end thereof to the opposite portion of the bend of the strip 2I and at its other end to one side of the voice coil 3.

It will be noted that in this case the signal source is directly connected to both terminals of the voice coil 3, the conductor 23 being connected to one terminal of the source, as well as a terminal of the voice coil 3. y

The prongs I2 and I3 terminate immediately adjacent the conical contacts I8. Furthermore, in this modication the insulation support I4 is not T-shaped, but instead has depending therefrom a resilient metallic forked prong 24. The upper end of the prong 24 is embedded within the support I4, the embedded end being connected by a conductor 25 to the terminals of the signal source and the voice coil 3 opposite to the terminals to which the conductor 23 is connected. The lower end of the prong 24 is forked, the pendulum extension 9 being disposed between the depending spaced ngers 26 of the forked end of the prong. About halfway between the ends of the prong 24 there are secured a pair of contact elements 21, each element 21 being secured upon the face of the prong 24 in such a manner that when the latter is displaced in a direction towards prong I2 or I3, an element 21 will make contact with a conical element I8.

In operation, therefore, the pendulum member 6 is adjusted for the necessary degree of slip on the shaft 5, and the prong 24 is made suiilciently resilient so that when the shaft 5 is actuated in either direction, as before, the frictional force developed between the friction disc portion 6 and the shaft 5 will be sufficient to move the extension 9 into contact with either finger 26 thereby forcing an element 21 into contact with a conical contact I8. Here, again, the forked prong 24 is made resilient enough to maintain the pendulum member 6 immobile when contact has been established between an element 21 and a Contact I8, and, additionally, to immediately restore the extension 9 of the pendulum member to its normal, intermediate position, when the shaft 5 is rendered immobile.

It will be seen that signal current will flow through the voice coil 3 whenever the extension 9 is in its normal, midway position, but as soon as the shaft 5 is actuated contact is immediately established between an element 21 and a conical contact I8, such contact resulting in the sh0rtcircuiting of the voice coil 3, by virtue of the flow of current from the signal source through conductors 23, 25 or conductors 25, 22 and 23.

It is pointed out that the invention is not limited to use with ani electrodynamic speaker, it being within the scope of the present invention to substitute an electromagnetic type of i speaker and even an electrostatic type of speaker. The fundamental idea involved is the same, and this comprises the requirement that the energizing current circuit of the reproducer be instantly interrupted, and maintaind in such interrupted position, at the moment the tuning shaft is actuated, and as long as it remains actuated. Again, it is not essential to the present invention that the manually-operable knob be affixed to the receiver panel in the usual manner, but it is well within the scope of the present invention, for example, to place the manually-actuable mechanism at a point remote from the receiver shaft, and coupled at said shaft to the remote manual mechanism, such coupling being for example a flexible mechanical coupling well known to those skilled in the art.

While I have indicated and described several systems for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. In combination with a radio receiver having a tuning element for selectively tuning said receiver, an output circuit for said radio receiver including a reproducing device, a knob for adjusting said tuning element, contacts and means whereby the rotation of said knob actuates the contacts for reducing the output of said reproducing device only during said rotation.

2. In combination with a radio receiver having a tuning element for selectively tuning said receiver, an output circuit for said radio receiver including a reproducing device, a knob for adjusting said tuning element, and means whereby the rotation of said knob reduces the output of said reproducing device only during said rotation.

- 3. In a signal amplifying system, the combination of signal amplitude limiting means, means movable in a given direction for adjusting said system, means responsive to a motion in the same direction of said adjusting means at all positions thereof for rendering said limiting means Veffective in said system and for rendering said limiting means ineffective upon cessation of` said motion.

4. A radio receiver having a tuning shaft, a rotary knob for operating said shaft, a normally open shunt switch in the loudspeaker circuit, and means whereby the rotary movement of said knob in either direction from any of its positions of rest automatically closes said switch for silent tuning.

5. A radio receiver having a tuning shaft, a rotary hand knob for actuating said shaft, a normally operative loudspeaker circuit, means for automatically rendering said circuit inoperative by the rotary movement of said knob in either direction, said means including connections whereby said circuit is automatically restored to operative condition when the knob is released, and means whereby said shaft remains stationary during the circuit-restoring operation of the released knob.

6. A radio receiver having a tuning shaft, a rotary hand knob for actuating said shaft, a normally closed loudspeaker switch, means for automatically opening said switch by the rotary movement of said knob in either direction, means whereby said switch is automatically closed when the knob is released, and means whereby said shaft remains stationary during the circuit-closing operation of the released knob.

7. A radio receiver having a rotary tuning element, means for actuating said tuning element, a normally operative loudspeaker circuit, means for automatically rendering said circuit inoperative by the rotary movement of the tuning element actuating means in either direction, said last mentioned means comprising a switch member associated with the loudspeaker circuit and a switch actuating member carried by the tuning element actuating means.

8. In combination with the voice coil of an electrodynamic loud speaker, a normally open switch connected in shunt with said coil, a shaft and a control knob aixed thereto adapted to be adjusted by rotational movement thereof to various tuning positions, and means mounted on said shaft actuated only during the rotational movement of said shaft between tuning positions for closing said switch to short-circuit the voice coil, said means having a radial projection which constitutes the switch-closing means.

9. In combination with the field coil of an electrodynamic loud speaker, a normally closed switch connected in series with said coil, a shaft and a control knob affixed thereto adapted to be adjusted by rotational movement thereof to various tuning positions, and means mounted on said shaft actuated only during the rotational movement of said shaft between tuning positions for opening said switch to open-circuit the eld coil, said means having a radial projection which constitutes the switch-opening means.

10. In combination with the energizing circuit of a loud speaker, a normally open switch connected in shunt with the circuit and including at least one resilient contact element, a shaft and a control knob affixed thereto adapted to be rotated to different tuning positions, and a switch-actuating member frictionally mounted upon said shaft for movement therewith only during the rotational movement of said shaft in either direction between tuning positions, said switch-actuating member provided with a radial projection arranged to coact with the resilient contact element whereby the normally open switch is closed to short-circuit the loud speaker energizing circuit.

11. In combination with the energizing circuit of a loud speaker, a normally closed switch connected in series with the circuit and including at least one resilient contact element, a shaft and a control knob aiixed thereto adapted to be rotated to different tuning positions, and a switch-actuating member frictionally mounted upon said shaft for movement therewith only during the rotational movement of said shaft in either direction between tuning positions, said switch-actuating member provided with a radial projection arranged to coact with the resilient contact element whereby the normally closed switch is opened to open-circuit the loud speaker energizing circuit.

12. A radio receiver having a rotary tuning element, means for actuating said tuning element, a normally operative loudspeaker circuit, means for automatically rendering said circuit inoperative by the rotary movement of the tuning element actuating means in either direction, said last mentioned means comprising a pair of spaced contacts which are electrically connected together and to but one side of the loudspeaker circuit, a resilient member electrically connectedv to the other side of said circuit and provided with contact means capable of contacting with one or the other of said pair of spaced contacts Where-- by said circuit is short-circuited, and means carried by the tuning element actuating means cooperatively associated with the resilient member.

13. A radio receiver having a rotary tuning element, means for actuating said tuning element, a normally operative loudspeaker circuit,

means for automatically rendering said circuit g inoperative by the rotary movement of the tuning element actuating means in either direction, said last mentioned means comprising a pair of spaced resilient arms which are electrically connected to opposite sides of the loudspeaker circuit, a Contact on each resilient arm, rigidly mounted contact means, said resilient arms normally urging their respective contacts in contacting relation with said rigidly mounted contact means whereby the loudspeaker circuit is normally closed, and means carried by the tuning element actuating means cooperatively associated with one or the other of said resilient arms, depending on the direction of rotation of the actuating means, to open-circuit the loudspeaker circuit between a resilient arm contact and the rigidly mounted contact means.

ERNEST A. ZADIG. 

